windows explorer stopped working

Try using System File Checker to scan your OS for missing/corrupt files, complete these steps:

Click Start, and then type cmd in the Start Search box.

In the results area, right-click cmd.exe, and then click Run as administrator. You will be prompted to type the password for an administrator account. Click Continue if you are the administrator or type the administrator password. Then, click Continue.

At the command prompt, type Sfc /scannow, and then press ENTER.

The scan may take some time, so be patient. Windows will repair any corrupted or missing files that it finds. If information from the installation CD is needed to repair the problem, you may be prompted to insert your Windows Vista CD.